Determine the survival and multiplication of the host and vector components of selected EK1 systems in commonly used sewage treatment processes to obtain baseline information and reference points for new and potentially safer EK2 systems. Determine the survival of the host and vector components of a variety of EK2 systems in commonly used sewage treatment processes in order to assess whether they meet the criteria specified in the NIH guidelines for EK3 status. Determine the capacity of vectors from the EK1 and EK2 systems to be transmitted to secondary bacterial hosts.